When river scientist Mike Joy skewered the "100% Pure" brand in November he was accused of economic treachery.

He had delivered the same message countless times, but for the second time his comments went international. Like colleagues who had had an over-loud argument at the Christmas party, Kiwis started fretting about what potential tourists might think.

The answer, fortunately, is probably not much, say the men leading our tourism branding efforts. It takes a long time to build a brand, and a long time to break it.

If New Zealand was a product, its brand would be the fifth-strongest in the world. That's according to Futurebrand, a company that ranks perceptions of the world's nations each year as if they were consumer products.

The judges canvass 3600 frequent travellers and talk to policy experts about such brand criteria as whether people know a country exists, what they know, and whether they like it.

In 2012, most of the big boosts and slides were easily traced to major world events. Italy and Spain fell after the euro crisis; Germany rose. Britain rose after it hosted the Olympics; the United States has been in freefall since the heights of Obama-mania.

Meanwhile, Down Under, New Zealand and Australia seemed to slip a little further off the judges' radar. New Zealand dropped two places overall, falling out of the top 10 for tourism for the first time in the report's eight-year history.

The judges said, despite big tourism spending, New Zealand and Australia had fallen slightly in the "consideration" stakes - meaning people were a little less likely to consider them as a place to visit, source products or invest.

The battle for recognition is constant, even in some of our biggest tourism markets.

In Japan, for example, we are such a tiny player that we could grow our share of outbound tourism significantly even as the Japanese economy sags, says Kevin Bowler, Tourism New Zealand chief executive. It takes a long time to change a national brand, he says.

The flipside is that it would take an "enormous shift" for New Zealand to lose its reputation for natural beauty. "You have to remember that once you get north of Cape Reinga or west of Taranaki, New Zealand doesn't really get a lot of attention."

Bowler says Tourism NZ can find no evidence at all that negative articles about New Zealand's environmental management affect the views of potential tourists.

He expects no fallout from the latest green debate. Bowler recounts how, a month after the deadly Christchurch earthquake, as many as one in four potential Australian tourists knew nothing of any shaking.

The quake had been the lead story on every Australian news channel for days.

The best available gauge of New Zealand's image with potential holiday-makers is the Active Considerer Monitor.

Tourism NZ commissions a continuous series of online polls about our perceived fun-ness, cleanliness, sustainability and so on among the major targets of our advertising spend - people with the time, money and desire to travel here.

The polls were not yet running in 2009, when Guardian environment writer Fred Pearce accused New Zealand of giving a "shameless two fingers to the global community" for having high greenhouse gas emissions per capita.

In May 2011, when BBC journalist Stephen Sakur used Mike Joy's statements to goad Prime Minister John Key about the state of our rivers, the radars showed nary a blip.

That is, the following quarter's result showed no significant change in the number of people who agreed New Zealand was clean and unpolluted, or managed its environment sustainably, in any of the big markets - Britain, the US, Australia, Germany, Japan and China.

As Fairfax has reported, the last major government study on the value of the clean, green brand in 2000 concluded it would decimate tourism from several major markets if New Zealand's environment was perceived as being degraded. But it also said the image was "separate from the reality of the state of our environment".

In other words, New Zealand had a buffer period during which its environment could degrade without it necessarily affecting our image. Exit polls suggest tourists leave New Zealand with excellent impressions of the environment and scenery, consistently rating them about nine out of 10.

That doesn't mean we can be complacent, Bowler says. "I'm not trying to suggest these (environmental debates) are unimportant and that we shouldn't have a high level of concern. But it does take a very long time to change the global image we project to the world."

"I don't think at the moment [the debate] is in the slightest bit damaging from an international point of view. I think when it would get damaging would be if visitors were starting to indicate that our environment was nowhere near as good as what they were expecting."

As head of the Tourism Industry Association, one might expect him to be defensive about New Zealand airing its dirty streams in public. Quite the opposite, he says.

"When a guy like Mike Joy puts his neck out and raises the debate, I'm saying listen to him . . . don't allow the debate to be deflected into a debate about a marketing brand."

This is what frustrates Snedden. In his view, green advocates risk undercutting their cause by hitching the debate to one area where he sees no discernible problem - tourists' and potential tourists' impressions of us.

Sniping about the accuracy of the marketing slogan has become a distraction from actual research showing we could manage precious resources much better, he says.

It is natural for people who are concerned about the environment to want to link the debate to the economy: it broadens their audience. And, as many have noted, Tourism NZ gave critics an excellent opening with its 100% Pure branding campaign, focusing heavily as it does on scenery and the environment.

But: "If it was just about the [100% Pure] marketing slogan, the result of the visitor experience monitors would lead you to believe that it is not a debate worth having, because the visitors are happy," he says.

In fact, failing to adequately protect freshwater and other assets will hurt much more than tourism in the long term, he says.

Then there's the global economy. As purse strings tighten in our traditional long-haul markets, New Zealand is relying increasingly on middle-class Chinese and Australians to fill the spending gap left by Brits and Americans.

The biggest driver of tourism is the economy of the outbound nation, says Peter Ellis, manager of tourism research and evaluation at the Ministry Business, Innovation and Employment.

There is not a thing New Zealand can do about that, which is why it is comforting that NZIER is predicting a structural shift in our tourism market to 2018 towards the comparatively strong economies of China and Australia.

Of the two countries, China has by far the biggest untapped potential: New Zealand already accounts for a huge share of Australian outbound tourism.

The NZIER forecasts form the economic "baseline" for tourism marketing efforts, assuming our share of tourists leaving each source country keep tracking along the same path as today, says Ellis.

The object of tourism marketing, obviously, is to improve on the baseline.

What does that mean for the way New Zealand brands itself? Well, the Chinese appear to rank "having fun" more highly than tourists from Western nations, and they perceive New Zealand could lift its game in that area, Tourism NZ says.

But the clean, green branding won't be going anywhere quickly. The top brand association potential Chinese tourists have with New Zealand is "getting in touch with nature".

TO SPEAK, OR NOT TO SPEAK, THAT IS THE ISSUE

Should scientists consider the economic fallout of their views? The prime minister's science adviser, Sir Peter Gluckman, no stranger to voicing a view based on his research, says there's no easy answer.

On one hand, "Why have a participatory democracy if a scientist is not allowed to advocate from his knowledge?"

On the other, "Scientists when they act as advocates for an issue are fundamentally no different than any other lobbyist.

If they are using their position as scientists to deliver that advocacy, they need to be careful to give a balanced view of what the data does and does not say."

Gluckman knows Mike Joy only slightly and didn't want to comment directly on his critique. But the New Zealand Association of Scientists leapt to Joy's defence when he was accused of ill timing.

"The clear statement is that the potential damage to New Zealand's reputation, and economic benefit of ‘big-spending American tourists' outweighs the need for truth in public debate.

This is an issue that the association takes very seriously," said NZAS president Shaun Hendy.

Gluckman noted that media commentary was a two-way street - sometimes scientists sought the media, but often journalists sought scientists who are subject matter experts or known for communicating well on certain topics.

"It would be horrible if every scientist was expected to be a robot," says Gluckman.

"I don't have a problem with a scientist saying 'I've done this work - this is what I know and this is what I don't know and for the following reasons I believe passionately that we should do this or that'."

Society does not have to listen. Contrary social or economic arguments may win the day, as with Gluckman's conclusion that the evidence supported putting folate in bread.

"It may be the most sensible option, but that doesn't mean governments will always follow science."